Facsimile (fax) machines and the fax transmissions originating from such machines are known. Such machines are typically used to transfer printed and graphical information over great distances via a public switch telephone network (PSTN).
Within a fax machine the printed or graphical information is typically converted into an electrical signal using an optical scanner. A sheet of paper containing the printed or graphical information is fed into a set of transport devices (e.g. rollers) within the fax machines which transports the sheet of paper past the optical scanner. The scanner rapidly scans the width of the sheet transverse to a direction of movement as the sheet is transported past the scanner. A modem within the fax machines converts the electrical signal from the optical scanner into a variable frequency, electrical signal typically in the audio range, for transmission through the PSTN.
At a fax receiver the variable frequency signal is converted into a variable direct current (DC) voltage which is then used to electostatically dispose a darkening agent (toner) on a received fax sheet in such a manner as to recreate the image detected by the scanner at the transmitting fax machines. The toner is then fixed to the sheet by the application of heat, or otherwise, to complete the process.
To initiate a fax transmission an operator enters a destination telephone number of the fax transmission and loads the material to be faxed into a paper tray on the transmitting fax machine. The transmitting fax then scans the faxed material into a memory in anticipation of transmission. Once the material to be faxed is loaded into memory, the transmitting fax machine seizes an interconnected telephone line and transmits the destination telephone number to a controller within the PSTN. The PSTN controller through a number of local and remote telephone switches, interconnects the calling fax to a target fax. A local PSTN controller notifies the target fax of the incoming call by causing a telephone associated with the target fax machine to ring. The target fax detects the electrical pulses of the ringing, seizes the telephone line and establishes a connection with the transmitting fax machine. The faxed information is then transferred from the transmitting to target fax machine. Upon completion of a transmission, a fax report is printed by the transmitting fax machine listing, inter alia, a target telephone number and number of pages transmitted.
While existing fax machines work well, the prior art has taught that a fax machine can not be relied upon where proof of delivery is required such as for notification of consumer product safety hazards or certain types of court documents. Where proof of delivery is required the prior art has taught that the only alternative is certified U.S. Mail or hand delivery. Because of the importance of certifying delivery of such documents a need exists for a method of certifying fax transmissions.